Unfortunately, an HDD can fail without warning as well (I speak from experience). Utilities such as SSD life (pro) that monitor the "health" of the SSD can offer some measure of reassurance.

HDD failures without any sort of warning are pretty rare, at least in my experience. Over at the XtremeSystems, where they're pushing SSDs to fail for endurance testing purposes, SSDs have died without generating any SMART errors or warnings.. Note also that none of them have failed in the much-heralded "read only" mode. They just died -- no data was retrievable.